Not Applicable.
The present invention relates in general to side object detection systems for motor vehicles, and, more specifically, to determining a location of objects within a detection zone based on a limited number of detection points from a remote sensor that provides an incomplete boundary of an object.
Automotive systems known as side object detection systems (SODS) utilize xe2x80x9cside-lookingxe2x80x9d remote sensors for such applications as blind-spot detection and lane change aid. These applications are designed to alert the driver to potential hazards, e.g., objects that may be located adjacent to the host vehicle. The remote sensors may employ radar transceivers, light sensors, ultrasonic sensors, and other technologies.
One objective of the side-looking sensors is to identify the presence and location of objects within a predetermined zone of interest adjacent to the vehicle. Radar sensors detect and locate objects by transmitting electromagnetic energy which reflects off of objects within the sensor field-of-view. The reflected signal returns to the radar sensor where it is processed to determine the round-trip travel time of the transmitted/received energy. The round trip travel time is directly proportional to the range of the target from the radar sensor. In addition to range determination, there are methods to determine azimuth (i.e. cross-range) location of detected objects such as multiple scanned/switched beams and mono-pulse implementations. Therefore, depending upon its complexity, the radar is capable of locating objects in both range and azimuth relative to the sensor location.
Based upon the reflected signals during a sampling of the entire field-of-view, a set of detection points is accumulated. Due to the nature of xe2x80x9creflectionsxe2x80x9d collected by a remote sensor (whether a radar, laser, ultrasonic, or other active sensor), the set of detection points is representative of only certain spots on the object or objects present in the sensor""s field-of-view. The detection points must be analyzed in order to determine what type of objects may be present and where such object is located.
Based on the type and location of detected objects, a blind spot detection or lane change aid system must decide whether a detection is one for which it should alert the driver. Under certain conditions, it may be undesirable to always generate an alert every time that any object is detected in the detection zone. For example, side-looking radar sensors will be subjected to reflections from common roadway structures such as guard-rails and roadside signs. These objects may not constitute a threat to which the driver desires to be alerted since they are stationary. However, due to the complexity of the driving environment, it has not been possible for a radar sensor to discriminate between the various driving scenarios without extensive processing and expensive sensor designs. It would be desirable to discriminate between objects for which an alert should or should not be provided using relatively simple sensors and without excessive computational resources.
Occupant safety systems are known that include pre-crash functions based on sensing an impending collision and taking advance actions to increase protection of the vehicle occupants. Potential pre-crash actions include pre-tensioning of seatbelts and adapting the deployment of airbags in response to the expected point of impact. Prior art pre-crash systems have employed forward-looking or rearward-looking radar wherein velocity of an object includes a radial component thereby permitting the detection and localization of objects based on Doppler measurements. In side-looking systems, any radial velocity is small and Doppler measurements are impractical. Nevertheless, the ability to determine a side location could be used to improve the pre-crash actions and to determine whether an object is in the predicted path of the vehicle (e.g., using steering angle information).
The present invention has the advantage of detecting a location of an object within a zone of interest to the side of a transportation vehicle using relatively simple and inexpensive remote sensors and signal processing.
In one aspect of the invention, a method is provided for classifying an object location of a 3-D object to a side of a transportation vehicle wherein the transportation vehicle moves along a front-to-rear directional axis and has a remote sensor mounted at a predetermined reference point. A set of detection points is identified substantially to the side of the transportation vehicle using the remote sensor. A detection point is found having a closest range to the vehicle reference point. The object is classified as on-center if a position Ynear along the directional axis corresponding to the closest-range detection point is within a predetermined threshold distance from a position Yzero along the directional axis corresponding to the predetermined reference point. If not on-center, then the object is classified as spanning if a first position Y1 along the directional axis and a second position Y2 along the directional axis are on opposite sides of the position Yzero. If not spanning, then the object is classified as front if any particular detection point is forward of the position Yzero. If not spanning, then the object is classified as rear if any particular detection point is rearward of the position Yzero.